As an encapsulating material for encapsulating photosemiconductor elements such as light emitting elements and light receiving sensors, a cured product of the material is generally required to have transparency, so that an epoxy resin composition obtained by using an epoxy resin such as a bisphenol A-type epoxy resin or an alicyclic epoxy resin and a curing agent such as an acid anhydride has been commonly used.
However, in recent years, luminance has been heightened in light emitting elements and use of light receiving sensors has become popularized in in-vehicle applications and as blu-ray pickups. Under the circumstances, as the epoxy resin composition for photosemiconductor element encapsulation, a transparent encapsulating material having a higher heat resistance and light resistance as before has been required.
For example, in the above epoxy resin composition for photosemiconductor element encapsulation, as a method for improving heat resistance or light resistance, there have been hitherto used: a method for elevating glass transition temperature (Tg) of a cured product thereof by using a polyfunctional epoxy resin (see Patent Document 1); and a method for suppressing light deterioration by light absorption by using an alicyclic epoxy resin (see Patent Document 2).
Patent Document 1: JP-A-2005-68234
Patent Document 2: JP-A-7-309927